Will tablets be a tweener?

One of the questions related to client computing that I've been exploring of late is whether we're likely to see a mainstream mobile device or devices emerge between a smartphone and an ultra-portable notebook.

My Illuminata colleague Jonathan Eunice and I debated this subject on a video recently--mostly in the context of long battery life, instant on/off mini-notebooks of various sorts. The HP Jornada 820 of the late 1990s is one possible prototype for such a device, suitably updated for a wirelessly connected world. The stillborn Palm Foleo is another take.

I'm perhaps more skeptical than my colleague that we'll see the right intersection of technologies, costs, and use cases to support a mainstream mobile--but not pocketable--computer that's not a full notebook but has other attributes that make it compellingly better for people on the go.

(This is the point where someone jumps up and yells "NETBOOKS!" To which my response is that Netbooks are not really a category. Leaving aside for the nonce an apparent weakening of their most faddish popularity, Netbooks are really just cheap notebooks. Low price is their distinguishing feature, not battery life or anything else that makes them particularly suited to throwing in a backpack. Even their weight is little different from the best of the ultraportable notebooks.)

Of course, in a sense, we have lots of tweeners today. We have digital cameras, portable gaming consoles such as the Nintendo DS, and e-ink based e-book readers like Amazon's Kindle. But these are all optimized for very specific purposes; they're in no sense general purpose computers or even subsets of computers optimized for mobility.

However, a recent post by ZDNet's Jason Perlow "Forget Kindle DX. How about the ZuneBook?" got me thinking. Might some form of  tablet one day be a tweener of choice?

Let me be crystal clear about one point. I'm not talking about tablet PCs as we know them today. They have their adherents but most people find that it's hard to use them for many of the things that PCs are good for (like writing using a keyboard) while simultaneously carrying over notebook baggage such as weight, relatively short battery life, longish boot times, and so forth.

Rather I'm thinking of something that is physically thin, light, easy to read in sunlight, instant on/off, multitouch screen, wirelessly connected using both Wi-Fi and cellular networks, and about the size of an 8.5-inch by 11-inch pad of paper. I imagine a software environment that isn't necessarily general purpose but could be extended to at least some degree. Google Android or Windows Mobile might be possibilities. Think of it as an e-book reader on steroids.

Such a device isn't possible today even if you leave out the question of what it would cost if it could theoretically be built. The display is the real killer. A color, e-paper, multitouch display is a few years out. OLEDs will improve on existing LCDs on several dimensions--notably, in this context, battery life and thickness. However, OLED technology still doesn't get you to the same easy-on-the-eyes-even-in-sunlight point and all-day-plus battery life as e-paper.

But it seems an interesting direction for device makers to explore. Once the foundation technologies are available, it's something that could deliver qualitatively different experiences than either a pocketable smartphone or a notebook with a keyboard. And that's the sort of compelling differentiation that a tweener device will need to make it big.